Hi,
I've been curious about the merits of running a library on its own SCSI
channel. I've seen a few comments about this in my recent posting:
Advice on a specs for a Sun
We've been having sporadic SCSI bus reset type problems that occur on
our Linux storage node box wherein the storage node simply looses
communication with the picker(s). Typically when this occurs,
/etc/LGTOuscsi/inquire will report all the drives on all the libraries,
but it will issue an error on the picker devices. We've been through
many patches, kernel upgrades, everything. We've checked the cables,
cards, you name it. The problem still exists.
What I'm wondering is if maybe the problem is being caused by the fact
that we're running two different libraries on the same server, or if it
might be the fact that in both cases, the devices for the pickers also
share the same SCSI card as at least two drives. Allow me to explain
below:
We're running two libraries on this Dell PC. One is a Storagetek L80
with 4 LTO (1st generation) drives. Two drives are daisy chained and
cable is connected to channel A on one dual-channel Adaptec SCSI card
LVD. The other two drives and the picker are daisy chained and cabled to
channel B. The library is properly terminated, latest firmware code, and
proper LVD cabling (not too long) as installed and then re-installed by
Storagetek. The second library is an ATL P1000 with 2 SDLT (1st
generation) drives. Both drives and the picker share one channel on the
second dual-channel Adaptec card. Admittedly, though, one of these cards
is a "true" Adaptec card, and the other is a DELL OEM Adaptec card.
We've already been through the BIOS upgrade on the "true" Adaptec.
I've not yet tested running just the Storagetek by itself without the
ATL library on there. I could do that by moving the ATL to another
machine and setup as temp storage node. We really need both libraries so
kind of a pain as the errors occur sporadically and is unpredictable.
Could go a week before problem returns. We would need another card to
test to see if running the picker on its own channel might fix things
since the other card would be needed for the other library. I don't see
any reason that two drives cannot share a channel. Maybe 3 would be
tugging on superman's cape, but 2 should not be a problem, right? I
mean, a channel is analogous to a separate bus, yes? And I don't see why
a picker could not share the channel, too, but maybe a picker and two
drives too much on one channel?
Does anyone think it's worth pursuing to have Storagetek come out and
configure Storagetek library to run on its own channel so not daisy
chained to any drive and then hook up its own cable to its own channel
on another card? Maybe I should try running just one library first?
Would greatly appreciate any help.
thanks.
George
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